Wheel/Rail force ground measurements of rail vehicles are very important to safety evaluation of rail vehicles. Since the strain of steel rails above sleepers is greatly affected by the support state of the sleepers, the wheel/rail vertical force applied to the rail located above the sleepers cannot be measured stably. The existing wheel/rail vertical force ground measurement is usually implemented by a discontinuous mid-span shear force method. For example, the current railway industry standard “Ground Measurement Method for Wheel/Rail Horizontal Force and Vertical Force” (TB/T 2489-94) in China provides that a wheel/rail vertical force is measured using a combination of two shear force measurement points with a spacing of 220 mm in the same mid-span of rail. On a conventional line, the mid-span shear force method generally can merely obtain a wheel/rail vertical force within a distance not greater than 10 cm, and the effective measurement scale is about 0.1 m.
The Chinese patent No. ZL 92228559.4 and entitled “Combined Device for Dynamic Measurement of Vertical Force” (abbreviated as “the 559 patent” hereinafter) employs two shear force sensors arranged in different mid-spans of rail and one or more weighing sensors which located between the two shear force sensors to form a wheel/rail vertical force measurement platform, and combines the outputs of the shear force sensors and of the weighing sensors of the measurement platform to obtain a wheel/rail vertical force applied to the entire measurement platform. However, when this existing ‘shear force+support force’ method is applied to the measurement of a wheel/rail vertical force, the length of a single platform (a unit measurement area) is limited by the wheel base of the rail vehicle, and there is one ineffective shear force measurement area whose length is close to the steel rail height, i.e., a shear force measurement transition area. Thus, the actual effective measurement scale is about 1-2 m. When “the 559 patent” is applied in the industry to perform a long-distance measurement, a plurality of continuously arranged unit measurement areas are employed, and adjacent unit measurement areas share an end shear force sensor to obtain a quasi-continuous wheel/rail vertical force. This requires a longer nominal measurement length to realize full coverage measurement to the circumference of a wheelset, and a spatial time sequence cannot be ensured for the circumferential geometry of the wheelset. Thus, the safety monitoring requirements of passenger trains and high-speed trains cannot be well satisfied.
One technically feasible long distance continuous measurement method for a wheel/rail vertical force is to continuously arrange a plurality of ‘shear force+support force’ unit measurement areas so that the effective measurement ranges of adjacent unit measurement areas can mutually cover each other. At this moment, the end shear force sensors of adjacent unit measurement areas cannot be shared. However, this method is high in cost, and the system reliability is reduced under equivalent conditions, thus being difficult to promote and apply.
The Chinese patent No. ZL 2009 1 0086149.5 and entitled “Continuous Measurement Method and Device for Wheel/Rail Vertical Force based on Steel Rail Strain” employs different strain combinations of steel rails, realizing long-distance continuous measurement of the wheel/rail vertical force. Although the implementation cost of this method is not high, the maintenance is inconvenient, thus currently being difficult to be widely applied in engineering.